Flotation cell



II I

I I Q o\ as I l 4 I 33 40 as July 28, 1942. A, w FAHRE'NWALD 2,291,031

FLOTATION CELL Filed Dec. 30, 1940 3 Sheets-Sheet 1 Snventor AR THUR W. FAHRE N WALD (Ittorncg July 28, 1942;

A. W. FAHRENWALD FLOTATION CELL Filed Dec. 30, .1940 3 Sheets-Sheet 3 l0! I4 I I00 v 99 33 ARTHUR W. FAHRENWALD 98 Bnventor provide an improved flotation cell for use a process,

Patented July 28, 1942 r UNITED STATES PATENT OFFICE FLOTATION CELL Arthur W. Fahrenwald, Moscow, Idaho Application December 30, 1940, Serial No. 372,262 14 Claims. (01 109-469) My present invention relates to improvements in flotation cells, of the type and nature employed in the treatment of crushed mineral substances for the separation and recovery of the more valuable content from the less valuable content.' It is well-recognized that the art of separating valuable minerals from extraneous substances, such as rock and the like, may be efiiciently practiced by following .the steps of the well-known flotation processes. According to the teaching of the flotation processes, finely crushed ore or pulp is introduced into a cell or tank, or a series of such structures, and is subjected to the beating action of. a rotary impeller. in the presence of a great amount of liquid matter which usually contains certain froth producing and mineral attracting agents. The beating action of the impeller causes a froth of fine bubbles to form and through the aflinity of the mineral values in the pulp for .the bubbles of the froth, which aflinity may be enhanced by the mineral attracting agents, the values .are caused to rise in the tank with the froth to the upper surface of the liquid, from which it may be removed by skimming or by overflowing along the edge of the tank.

It is an important objectof my invention to in such which cell may be used-singly, in pairs, or in any series or parallel arrangement of a multiplenumber' of cells that may be deemed necessary 'or advisable.

It is another object of my invention to provide a flotation cell in which there is a positive pulp circulation'as distinguished from those cells in which the pulp is normally disposed in the cell and is merely treated and'circulated by the currents rather than positively.

It is a further object of my invention to provide a pulp flow conduit system for fiotationcells which enhances the positive pulp circulation deemed necessary to the adequate practice of flotation processes.

Still another object of my invention resides in providing in a flotation cell pulp level control means which may be adapted for variable adjustment according to the desires of the operator or for the necessities of adequate treatment.

Still another object of my invention relates to providing in a flotation cell means for feeding the pulp to the impeller and for withdrawing the over flow liquids, which means are disposed centrally of the cell.

- Another object of the invention has been to provide in a flotation cell adit and exit ports a swirl destroying means to eliminate undesirable features of other developments.

Still another object of my invention has been the provision of a pulp conduit system which may through the median of a flotation. cell with certain portions illustrated in elevation.

Figure 2 is a similar vertical sectional view taken'in a plane at right angles to that of Figure having centrally located Figure 3 is a horizontal sectional view taken on line 3-3 of Figure 1,

Figure 4 is a view partially in section and partially in elevation taken on line 4-4.013 Figure 2, V

Figure 5 is an elevationa view of a divider bushing used in the lower portion of the vertical conduit tube,

Figure 6 is a sectional horizontal view taken on line 6--G of Figure 1,

Figure 1 is a with'portions hidden indicated by dashed lines, and

Figured is a fragmentary sectional view similar to Figure 1, but illustrating a modified form of my invention.

The numeral Ill designates a bottom wall of a tank cell having the side wall l2 in the form of 7 my invention illustrated. In the drawings the tank is shown as being formed in a circular shape, but it is to be understood that my invention may be employed with equal purpose in a square tank which may be used singly or in any multiple ar-' rangement of cells deemed advisable. I

In the circular form of the tank illustrated in the drawings an encircling launder or trough I4 is employed which has the relatively high portion l5 and a lower portion I6 that has a discharge spout Ill. The trated as being supported upon suitable .channeled supporting members 20.

A wear-resisting plate 22 is fitted into the bottom of the tank and a central hub 23 having the opening 24 passes through an opening in the plan view of the top of an impeller tankin Figures 1 and 2 is illusradial of the center of the tank, is a series of perforate anti-swirl baffles 28 which may be ar-- ranged in the tank in any suitable manner and serve to break up the more violent currents. By destroying the swirl, the plates 28 permit the froth or bubbles formed in the-agitation of the solution to rise and to carry with them the mineral values which are being separated from the ore pulp.

A riser conduit 38 is supported within the tank by means of a pair of arms 32-32 which are secured to the outer walls as indicated at 33a in Figure 2. This riser conduit may be formed of sheet metal, or it may be fabricated in any manner deemed advisable. Fabrication by welding is one of the more economical methods and lends itself well to use in this type of machine.

Extending outwardly from either side of the riser conduit is a feed conduit 33 and a discharge conduit 34. These conduits extend into fairlyclose relationship with the inlet tube 38 and the outlet tube 38, respectively. The tubes 38 and 88 are inserted through the wall of the tank and may be welded in place. Preferably they should aline with the tubes 33 and 34. A suitable Joinder between the tubes 33-38 and 34-38 iseflected by wrapping the joint with a piece of belting or canvas 40 which is to be retained in place by an.

encircling wire 4|.

Fitted into the lower end of the conduit 39 is the conduit divider member 42 which has an upper sloping wall 44 and a side-port 46; The port 48 registers with the feed conduit 33 and material passing through the conduit 32 and the port 46 strikes against the irmer face of the sloping wall 44 and is deflected downwardly. In the frllopiisg wall 44 is a hub 48 having a central open- Rising above the tank are angle support members 50-48 which are joined together by means spaces 11 are provided between'the outer wall of the member and the inner wall of the memberfli. Spacer elements 18 effectively support these two elementsin their spaced-apart relationship. 4

Within the inner, upper end of the riser conduit 38 is disposed an extension conduit 88 which has a pair of upstanding elevator arms 8 l--8l.

, Behind the plate 52 is a web plane 82 which is supported by means of legs 84 from the rear edge of the cell wall. Upon the legs 84 is provided a motor mounting plate 88.

A pair of elevating members preferably oflset levers 88 are pivoted at 88 to the plate 82 and their offset portions permit them to substantially enclose the quill 54. Their ends opposite the pivot point join and are shaped to form the bandle 88. Pins 82 connect the arms 8| to the members 88 and raising or lowering swinging movement of the member 88 will cause the extension conduit to raise or lower in the upper end of the riser conduit to vary the overflow level of the liquid within the cell or tank.

A pair of angle members are secured to the froth shield 16 and by means of holes a pin 96 is caused to engage into a suitable hole in the handle end of the lever 88 to hold the extension conduit in an adjusted position.

In Figure 8 I illustrate a modified form of my invention wherein a passage 88 is provided in the conduit divider member and a nipp e 88 communicates from the passage to a coupling I08 and a riser tube llll extends above the liquid and froth levels of the tank. In this form of the invention the essential feature is the provision of an auxiliary vent to provide additional air for the destruction of a portion of the vacuum created by the impeller during its rotary motion.

of a plate 52 -to form an impeller shaft bearing support or super-structure. To the plate 52 is mounted a bearing quill 54 designed and adapted to receive and support the impeller shaft 58. On the upper end of the impeller shaft 56 by means of the hub 58 is mounted a relatively large sheave 68; Suitable driving means forming a source of power not shown herein will cooperate with the sheave to rotate the impeller shaft.

The impeller shaft is best seen in Figure 1 to be sectional and its lower end terminates in a flange 82. An auxiliary shaft member, 64 is flanged at 86 and the flanges 82 and 86 are joined to attach the extension. to the main portion of the shaft 58. On the lower end of the impeller shaft is mounted an impeller disc 68 which has spokes 69 connecting the hub I8 to the disc 88. On the lower face of the disc are a multiple number of impeller blades 12 which, as may best be seen in Figures 1 and 2, are disposed in close proximity with the upper face of the wear Plate 22.

It will be seen that pulp passes through the tube 33, the port 46, and is deflected downwardly by the underface of the wall 44. The pulp will pass through the opening 14 between spokes of the disc and down to a point where it can be acted upon by the impeller blades 12 in their rotary motion.

Encircling the upper end of the riser conduit 38 is a froth shield I6 which is of a diameter suf- Method of operation of a series of different types of mineral-bearing pulp-treating machines. It is customary to arrange the flotation cell or cells, as the case may be, so that material that is introduced to the flotation cell is that which has Just previously been treated in a conditioner. The material flowing from the conditioner in' such a case would enter-the inlet conduit 36 and pass into the feed conduit 32. It would include a certain quantity of liquid and would flow, usually by gravity, with a fairly rapid advancing speed. y

I The material would be deflected downwardly by striking the under side of the sloping face 44. It is'thus fed to the upper face of the rotating impeller disc 88 and passes through the opening 14 between the spokes 88 into the central area of the impeller and the upper face of plate 22. The impeller is rotated at a relatively high speed and through centrifugal force the material is urged outwardly between the blades and thrown against the outer wall I! of thecell. The action of the rotating impeller also creates a vacuum in its center which tends, to enhance the incoming flow of pulp to the' impeller. At the same time flciently larger than the conduit so that sectional 1 the tank solution is aerated.

The anti-swirl baffles tendto destroy the swirl and to eliminate the circular movement of the liquid and the pulp in the cell, and as the aerated pulp strikes the baflies 28 its rotary motion is stopped and such bubbles as have been formed will begin to ascend in the solution in the tank. The tank is fllled with liquid to a level governed by the flow extension conduit Ill, if such an adjustable conduit is used, or by the level of the top edge of the riser conduit 30.

As the bubbles formed in the pulp and solution rise, they carry with them mineral values from the ore pulp which are attracted by the skin of such bubbles. In this manner an accumulation of froth forms on the top surface of the liquid within'the tank, and through the continuous operation of .the impeller and the continuous feed of additional pulp the mineral-laden heavy froth is caused to overflow the edge ofthe tank wall proper and into the launder provided by elements l4, I5, and H3. The launder has a sloping bottom, as shown in the circular form of the invention illustrated in the drawings forming a part of this specification, which leads the froth and the mineral carried thereby downward to the discharge spout l8 from whence it is removed from further treatment according to the practice of the process. I

The overflow solution in the tank or cell passes through the openings 11 and enters the riser con-' duit 30 at its upper lip or edge and descends until it contacts and is deflected by the upper face of the sloping wall 44, by which means it is deflected to the left in Figure l and into the discharge conduit 34, thence to the outlet tube 38 for re-treatment at other stages in therecovery process.

By means of the extension conduit 80, the pulp level is controlled within the cell or tank and this level can be changed, as can be seen in Figures 2 and 4, where by withdrawing the pin 96 and by grasping the handle 9!) the elevating'lever 88 can be raised or lowered to a new adjusted position. This adjustment can be effected during the operation of the machine without the necessityof a shut-down or an interruption of the treatment process.

Normally the machine will draw its own air. In other words, sufiicient air will be sucked in with the incoming stream of aqueous pulp so that the beating action of the impeller will thoroughly aerate the solution and the pulp. I e In certain instances it is deemed advisable to provide auxiliary air inlet means, such as through the passage 98 to which is attached the inlet tube IM that rises above the liquid and froth level of the cell and permits an inward flow of air when sub-atmospheric pressure is obtained within the chamber of member 42. Suitable control means for the flow of air through the tube llll, of course, could be used, such as a valve or the like to limit the air flow.

Unlike the flotation cells of the type in which the weir and baflle pulp level control is used, my cell has no cross currents, nor will the pulp short circuit from cell to cell and be inadequately aerated. The solution is completely, treated ac-- cording to-the principal purposes of the cell. In a machinesuch as mine it will be seen that each bit of pulp introduced into the cell has the same opportunity of being attracted by therising bubbles which form the froth, and that each bit travels the same distance from inlet to outlet. In this way a maximum of treatment may be obtained. This extremely worthwhile advantage is gained principally through the use of the centrally located pulp feed and discharge means comprising the feed conduit 32, the member 42, the riser 30, and the discharge conduit 34, through which passes the rotating impeller shaft. It is the ideal pulp adit and exit arrangement because it is located in the center of the cell. To locate such means at any other place in the cell is fundamentally wrong and only rough, ineflicient treatment is obtained by such other arrangements.

The wear-resisting flange 22 in the bottom of the tank protects the bottom of the tank and serves as a receiving surface for the inflowing pulp. Normally the bottom of the impeller blades I2 rotate in close proximity to the upper face of the plate 22 so that the fullest amount of material is acted upon by the impeller blades.

It will be understood and it is here again pointed out, that while in the drawings forming apart of this specification the cell structure is shown as circular, it is equally within the principles of my invention to employ a rectangular or other cell shape, according to the exigencies to be met, or the desires of the mill designer. Also these cells may be used either singly or in any multiple arrangement.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A flotation cell comprising a liquid-enclosing tank having adit means and exitwmeans for solutions to be treated and'froth-removal means;

an impeller in said tank for agitating solutions tank having adit means and exit means .for solu-.

tions'to be treated and froth-removal means; an impeller in said tankl for agitating solutions therein and including rotating means; a riser conduit supported in said tank and above said impeller and having a divider member in the lower portion separating the conduit into an upper and a lower chamber; a froth shield surrounding the upper end of said riser conduit in spaced relation thereto and extending above the froth level of said tank; a feed conduit associated with said adit means and the. lower chamber in said riser conduit to introduce pulp-bearing solution to said impeller; and a discharge conduit associated with the upper chamber of said riser conduit and said exit means to convey away the overflow solution.

3. A flotation cell comprising a ing tank having adit means and exit means for solutions to be treated and froth-removal means; an impeller in said tank for agitating solutions therein and including rotating means; a'riser conduit supported in said tank and above said impeller and having a divided member in the lower portion separating the conduit into. an up- "per and a lower chamber; an extension conduit to convey away the overflow solution.

4. A flotation cell comprising a liquid-enclosing tank having'adit means and exit means for solutions to be treated and froth-removal means; an impeller in said. tank for agitating solutions liquid-enclo'stherein and including rotating means; a riser conduit supported in said tank and above said impeller and having a divider member in the lower portion separating the conduit into an upper and a lower chamber; a froth shield surrounding the upper end of said riser conduit in spaced relation thereto and extending above the froth level of said tank; an extension conduit in the upper end of said riser conduit; a feed conduit associated with said adit means and the lower chamber in said riser conduit to introduce pulp-bearing solution to said impeller; and a discharge conduit associated with the upper chamber of said riser conduit and said exit means to convey away the overflow solution.

5. A- flotation cell comprising a liquid-enclosing tank having adit means and exit means for solutions to be treated and froth-removal means; an impeller in said tank foragitating solutions therein and including rotatingv means; a riser conduit supported in said tank and above said impeller and having a sloping divider plate in the lower portion separating the conduit into an upper and a lower chamber; a feed conduit associated with said adit means and the chamber formed below underside of said sloping divider plate in the riser conduit to introduce pulp-bearing solution to said impeller; and a discharge conduit associated with the upper chamber of said riser conduit and said exit means to convey away the overflow solution.

6. A flotation cell comprising a liquid-enclosing tank having adit means and exit means for solutions to be treated and froth-removal means; an

impeller in said tank for agitating solutions P therein and including rotating means; a riser conduit supported in said tank and above said impeller; a conduit divider member in the lower portion of said riser conduit including an angularly sloping divider wall separating the conduit into an upper and a lower chamber; a feed conduit associated with said adit means and the lower chamber in said riser conduit to introduce pulp-bearing solution to said impeller; and a discharge conduit associated with the upper chamber of said riser conduit and said exit means to convey away the overflow solution.

'7. A flotation cell comprising a liquid-enclosing tank having adit means and exit means for solutions to be treated and froth-removal means; an impeller in said tank for agitating solutions therein and including rotating means; a riser conduit supported in said tank and above said impeller; a conduit divider member in the lower portion of saidriser conduit including an angu- Y 'larly sloping divider wall separating the conduit into an-upper and a lower chamber; a froth shield surrounding the upper end of said riser conduit in spaced relation thereto and extending above the froth level of said tank; a feed conduit associated with said adit means and the lower chamber in said riser conduit to introduce pulp-bearing solution to said impeller; and a disinto an upper and a lower chamber; an extension conduit in the upper end of said riser conduit; a feed conduitassociated with said adit means and the lower chamber in said riser conduit to introduce pulp-bearing solution to said impeller; and a discharge conduit associated with the upper chamber of said riser conduit and said exit means to convey away the overflow solution.

9. A flotation cell comprising a liquid-enclosing tank havingadit means and exit means for solutions to be treated and froth-removal means; an impeller in said tank for agitating solutions therein and including rotating means; a riser conduit supported in said tank and above said impeller; a conduit divider member in the lower portion of said riser conduit including an angularly sloping divider wall separating the conduit into an upper and a lower chamber; a froth shield surrounding the upper end of said riser conduit in spaced relation thereto and extending above the froth level of said table; an extension conduit in the upper end of said riser conduit; 9. feed conduit associated with said adit means and the lower chamber in said riser conduit to introduce pulp-bearing solution to said impeller; and a discharge conduit associated with the upper chamber of said riser conduit and said exit means to convey away the overflow solution.

10. A flotation cell comprising a liquid-enclosing tank havi'ng adit means and exit means for solutions to be treated and froth-removal means;

7 an impeller in said tank for agitating solutions charge conduit associated with the upper chamber of said riser conduit and said exit means convey away the overflow solution.

8. A flotation cell comprising a liquid-enclosing tank having adit means and exit means for solutions to be treated and froth-removal means; an impeller in said tank for agitating solutions therein and including rotating means; a riser conduit supported in said. tank and above said" impeller; a conduit divider member in the lower portion of said riser conduit including an angu-, larly sloping divider wall separating the conduit therein and including rotating means; a riser conduit supported in said tank and above said impeller; a conduit divider member in the lower portion of said riser conduit including an angularly sloping divider wall separating the conduit into an upper and a lower chamber; a vent tube communicable with the chamber formed below underside of said sloping .divider wall; a feed 'conduit associated with said adit means in said riser conduit to introduce pulp-bearing solution to said impeller; .and a discharge conduit associated with the upper chamber of said riser conduit and said exit means to convey away the overflow solution.

11'. In a flotation cell, a riser conduit divided into super-imposed chambers, means for feeding pulp to the lowermost of said chambers, said lowermost chamber having means for introducing pulp into the cell, said uppermost chamber being adapted to receive outgoing pulp from said cell, a shield around the upper end of the riser conduit and extending above the froth level of the cell and adapted to permit the passage of pulp from the cell to the uppermost chamber of the riser conduit, and means for conveying pulp from the uppermost chamber outside the cell.

' 12. In a flotation cell, a riser conduit divided into superimposedchambers, means for feeding pulp to the lowermost of said chamber, said lowermost chamber having means for introducing pulp into the cell, the uppermost chamber being adapted to receive outgoing pulp from said cell,

and means for conveying pulp received in said defining the pulp level in said cell and for receiving the outgoing pulp therefrom, said last mentioned means being adapted for variable vertical positioning in said cell, and means for conveying pulp from the uppermost chamber outside the cell.

14. In a flotation cell, a riser conduit divided into superimposed chambers, means for feeding pulp to the lowermost chamber, said lowermost chamber having means for introducing pulp into the cell, said uppermost chamber having means defining the pulp level in said cell and for receiving the outgoing pulp therefrom, said last mentioned means being adapted for variable vertical positioning in said cell, a shield around the upper end of the riser conduit and extending above the froth level of the cell and adapted to permit the passage of pulp from the cell to the uppermost I chamber, and means for conveying pulp from the uppermost chamber outside the cell.

ARTHUR W. FAHRENWALD. 

